Problem: Is ${90811}$ divisible by $4$ ?
Answer: A number is divisible by $4$ if the last two digits are divisible by $4$ . [ Why? We can rewrite the number as a multiple of $100$ plus the last two digits: $ \gray{908} {11} = \gray{908} \gray{00} + {11} $ Because $90800$ is a multiple of $100$ , it is also a multiple of $4$ So as long as the value of the last two digits, ${11}$ , is divisible by $4$ , the original number must also be divisible by $4$ Is the value of the last two digits, $11$ , divisible by $4$ No, $11$ is not divisible by $4$, so $90811$ is also not divisible by $4$.